The present invention pertains to CCIS data transmission between data terminal equipment and a CCIS central processing unit and more particularly to data collection of regularly scanned input/output sources intermingled with randomly generated high priority data.
Data transfer between a CPU and a plurality data terminal equipment is typically accomplished via a buffering array. The CPU can then examine each of the number of buffers and transfer data on a cyclic or scanning basis.
In a CCIS (common channel interoffice signaling) configuration, data messages representing various events in the processing of trunk telephone traffic are transmitted via the data terminal equipment. Typical scanning type operation is adequate to provide the central processing unit of a CCIS sub-system with adequate response time for the transmission or the return data message. However, certain telephony events such as answer signaling require CPU response within 100 microseconds. These response times are much more rapid than a single CPU can scan a number of such data sources. In telephone signaling, the loss of such a signal can result in loss of the telephone call itself and more importantly in loss of revenue for the telephone call to the telephone operating company.
Accordingly, it is the object of the present invention to provide a CCIS data collection system where a single operating CPU interfaces with a plurality of terminal equipments on a scanning basis and simultaneously providing for the immediate transfer of data for certain time critical events.